The present invention relates to a gamma camera system used in medical examination, and in particular to the gamma camera system for single photon emission computed tomography (single photon ECT or SPECT), etc. performing dynamic study.
So far, diagnoses with a gamma camera system such as a SPECT apparatus have been known as one means for diagnosing the function of a patient's organ and/or tissue. Amongst such diagnoses, a dynamic study of imaging the change of such function in a specific slice over time has particularly become an indispensable means.
In this dynamic study, a detector is rotated about a diagnostic portion of a patient continuously N times (N is a positive integer: one rotation is referred to as "one repeat") and detects .gamma.-ray radiated from a radioisotope (RI) injected into a patient, thereby acquiring a plurality of sets of repeat data for N-time rotation. One repeat data consists of one set of position data (i.e. projection data) obtained at every predetermined rotation angle during one time of rotation of the detector.
When a plurality of sets of repeat data has been obtained for N-time rotations, image reconstruction and/or multiplanar reconstruction (i.e., obtaining a cross-section image in an arbitrary direction from a three-dimensional image data that had been once acquired) are carried out based upon these data. In this time, a reference image is displayed on a monitor in the first place.
As a method for selecting this reference image, known is a method to designate, as a reference data, the position data for a predetermined fixed repeat (the second repeat or the third repeat, for example) and display this reference data. Also known is a method where an operator observes the images reconstructed and displayed for each repeat and searches the one considered to be the most optimal for the reference data.
When the reference image is displayed in these manners, an operator designates a scope of image reconstruction and/or a range and angle of multiplanar reconstruction with a cursor on the monitoring image. After this designation has been completed, the sets of all the repeat data are processed under the same conditions (scope, angle, etc.) as the ones designated for the reference image and are subjected to the image reconstruction and/or multiplanar reconstruction.
In the above-described prior art, however, there was a problem of inaccuracy and operation inefficiency in cursor setting necessary for image reconstruction and/or multiplanar reconstruction.
The reason is as follows. Generally, the data collection begins on the administration of RI in the dynamic study of SPECT. The RI accumulates on a target organ over a certain period of time and is excreted thereafter. For the accurate cursor setting required is the quality reference image.
Nevertheless, with the aforementioned conventional method (the first-described one), there is no guarantee that the reference image with the predetermined fixed repeat data is always of high quality. Especially, when the earlier repeat data such as the first repeat data is employed, the reference image is often reconstructed even before the RI accumulates on the target organ, thus being of low quality. Therefore, the cursor setting accuracy may be lowered and the designation as to the image reconstruction and/or multiplanar reconstruction could not be executed as desired.
To avoid this disadvantage, the operator may watch a monitor screen and search a reference image displayed thereon without predetermining a repeat as described above. This method, however, requires a great deal of labor and time, thus resulting in low operation efficiency. Further, since this method burdens the operator with much monitoring operation, it brings a problem that the diagnosis efficiency is forced to be lowered in total.